scholarly journals Study of patterned GaAsSbN nanowires using sigmoidal model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sean Johnson ◽  
Rabin Pokharel ◽  
Michael Lowe ◽  
Hirandeep Kuchoor ◽  
Surya Nalamati ◽  
...  
Keyword(s):  
Spectral Shift ◽  
Length Variation ◽  
Dilute Nitride ◽  
Growth Trend ◽  
Sigmoidal Model ◽  
Pitch Length ◽  
N Incorporation ◽  
Highly Mismatched Alloys ◽  
Bandgap Tuning ◽  
Sigmoidal Growth

AbstractThis study presents the first report on patterned nanowires (NWs) of dilute nitride GaAsSbN on p-Si (111) substrates by self-catalyzed plasma-assisted molecular beam epitaxy. Patterned NW array with GaAsSbN of Sb composition of 3% as a stem provided the best yield of vertical NWs. Large bandgap tuning of ~ 75 meV, as ascertained from 4 K photoluminescence (PL), over a pitch length variation of 200–1200 nm has been demonstrated. Pitch-dependent axial and radial growth rates show a logistic sigmoidal growth trend different from those commonly observed in other patterned non-nitride III–V NWs. The sigmoidal fitting provides further insight into the PL spectral shift arising from differences in Sb and N incorporation from pitch induced variation in secondary fluxes. Results indicate that sigmoidal fitting can be a potent tool for designing patterned NW arrays of optimal pitch length for dilute nitrides and other highly mismatched alloys and heterostructures.

Materials Study of the Competing Group-V Element Incorporation Process in Dilute-Nitride Films

2009 ◽  
Vol 1202 ◽  
Author(s):  
Wendy L. Sarney ◽  
Stefan P. Svensson
Keyword(s):  
Light Element ◽  
Dilute Nitride ◽  
X Ray Diffraction ◽  
Ir Detector ◽  
Group V ◽  
Conflicting Information ◽  
Transmission Electron ◽  
Characterization Studies ◽  
N Incorporation ◽  
Lattice Matched

AbstractThe incorporation of small amounts of N into III-V antimonide-containing semiconductor alloys allows a drastic expansion of available wavelengths for infrared (IR) detector applications. Quaternary films containing three group-V elements can be lattice matched to the most prevalent substrates for IR applications, such as InAs, GaAs, and GaSb. It is not trivial to incorporate N while maintaining the high crystalline quality required for IR devices. Current materials characterization studies of dilute-nitride films consisting of more than two group-V elements has yielded conflicting information related to their competing behavior and the extent of N incorporation. Due to challenges related to light-element microanalysis for many characterization techniques, and the small concentrations of N involved, it is difficult to quantify the amount of N incorporated into dilute-nitride films. In this study, we use transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and x-ray diffraction (XRD) to study the incorporation behaviors of the competing group-V elements in InAsSbN films.

The "spectral shift" phenomenon of chloroquine

1966 ◽  
Vol 93 (1) ◽  
pp. 123-128 ◽  
Author(s):  
W. M. Sams
Keyword(s):  
Spectral Shift

On the Crystal Chemistry of Inorganic Nitrides: Crystal-Chemical Parameters and Opportunities in the Exploration of Their Compositional Space

2020 ◽  
Author(s):  
Olivier Charles Gagné
Keyword(s):  
Functional Properties ◽  
A Priori ◽  
Lone Pair ◽  
Length Variation ◽  
Electronic Effects ◽  
Statistical Knowledge ◽  
Redox Active ◽  
Multiply Bonded ◽  
Jahn Teller ◽  
Compositional Space

The scarcity of nitrogen in Earth’s crust, combined with challenging synthesis, have made inorganic nitrides a relatively-unexplored class of compounds compared to their naturally-abundant oxide counterparts. To facilitate exploration of their compositional space via <i>a priori</i> modeling, and to help <i>a posteriori</i> structure verification not limited to inferring the oxidation state of redox-active cations, we derive a suite of bond-valence parameters and Lewis-acid strength values for 76 cations observed bonding to N<sup>3-</sup>, and further outline a baseline statistical knowledge of bond lengths for these compounds. We examine structural and electronic effects responsible for the functional properties and anomalous bonding behavior of inorganic nitrides, and identify promising venues for exploring uncharted compositional spaces beyond the reach of high-throughput computational methods. We find that many mechanisms of bond-length variation ubiquitous to oxide and oxysalt compounds (e.g., lone-pair stereoactivity, the Jahn-Teller and pseudo Jahn-Teller effects) are similarly pervasive in inorganic nitrides, and are occasionally observed to result in greater distortion magnitude than their oxide counterparts. We identify inorganic nitrides with multiply-bonded metal ions as a promising venue in heterogeneous catalysis, e.g. in the development of a post-Haber-Bosch process proceeding at milder reaction conditions, thus representing further opportunity in the thriving exploration of the functional properties of this emerging class of materials.<br>

A Hydrogen Bond Between Linear Tetrapyrrole and Conserved Aspartate Causes the Far-Red Shifted Absorption of Phytochrome Photoreceptors

2020 ◽  
Author(s):  
Egle Maximowitsch ◽  
Tatiana Domratcheva
Keyword(s):  
Hydrogen Bond ◽  
Light Adaptation ◽  
Positive Charge ◽  
Pyrrole Ring ◽  
Md Simulations ◽  
Spectral Shift ◽  
Specific Domain ◽  
Study Guides ◽  
Rational Engineering ◽  
Tuning Mechanism

Photoswitching of phytochrome photoreceptors between red-absorbing (Pr) and far-red absorbing (Pfr) states triggers light adaptation of plants, bacteria and other organisms. Using quantum chemistry, we elucidate the color-tuning mechanism of phytochromes and identify the origin of the Pfr-state red-shifted spectrum. Spectral variations are explained by resonance interactions of the protonated linear tetrapyrrole chromophore. In particular, hydrogen bonding of pyrrole ring D with the strictly conserved aspartate shifts the positive charge towards ring D thereby inducing the red spectral shift. Our MD simulations demonstrate that formation of the ring D–aspartate hydrogen bond depends on interactions between the chromophore binding domain (CBD) and phytochrome specific domain (PHY). Our study guides rational engineering of fluorescent phytochromes with a far-red shifted spectrum.

Pakistan and the World Economy (Distinguished Lecture)

1998 ◽  
Vol 37 (4I) ◽  
pp. 181-201
Author(s):  
John Williamson
Keyword(s):  
Direct Investment ◽  
World Economy ◽  
Balance Of Payments ◽  
Engineering Industry ◽  
The European Union ◽  
Growth Trend ◽  
Difficult Situation ◽  
Financial Investment ◽  
The World ◽  
Deep Integration

This paper aims to explore Pakistan's geo-economic options in the difficult situation that confronts following the easing of sanctions, which added acute balance of payments pressures to its existing ailments of near-stagnant exports, a lower growth trend than in preceding decades, an unattractive climate for foreign investment, and weak social indicators. The first question explored is whether Pakistan has any opportunity of participating in a regional trade grouping. It is argued that the only conceivable way of achieving this would involve the development of SAARC, which would demand a profound transformation of Indo-Pakistani relations (though one no more profound than that realised in Franco-German relations since the founding of what is now known as the European Union). One benefit of achieving deep integration through SAARC is that this would create the possibility of Pakistan developing a serious engineering industry far more rapidly than will otherwise happen. In the absence of deep integration in SAARC, it is argued that Pakistan's best option would be a policy close to unilateral free trade, so as to place it in a position to take advantage of whatever the next generation of labour-intensive activities demanded by the world economy proves to be. Under either of those scenarios, the reestablishment of a dynamic industrial sector will require the maintenance of a competitive exchange rate, something that, it is argued, is not necessarily guaranteed by floating. The paper also discusses the role of inward direct investment in contributing to the export success of East Asia, and considers whether the expatriate Pakistani community might be capable of playing a role comparable to that played by the overseas Chinese in nurturing the Chinese export expansion of the last two decades. It is suggested that such a hope was set back by the extra-legal attempt to renegotiate power tariffs with the independent power producers in the course of 1998, and that Pakistan needs to become a country of laws rather than discretion if foreign investors, including expatriate Pakistanis, are ever to find the country an attractive export platform. While more inward direct investment would almost certainly be beneficial, the same is not true for inward financial investment, where too large an inflow can easily expose a country to very significant risks, as the East Asian crisis showed. In the long run, Pakistan needs to be prepared to repel excessive capital inflows if they materialise; but its immediate problem is still balance of payments pressure, and this seems to demand targeting a major and sustained improvement in the current account over the next several years.

Research on the Marketing Strategy of Online Education -- Taking New Oriental as an Example

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Jialu Chen ◽  
Yingxiao Han ◽  
An Li
Keyword(s):  
Online Learning ◽  
Online Education ◽  
Online Teaching ◽  
Large Scale ◽  
Target Market ◽  
Growth Trend ◽  
Continuous Growth ◽  
Financial Investment ◽  
Marketing Mode ◽  
Marketing Costs

In recent years, with the development of society and the progress of science and technology, online learning has penetrated into people's daily life, and people's demand for high-quality curriculum products is more and more strong. From a macro perspective, the continuous growth of national financial investment in education, the continuous upgrading of China's consumption structure, the development of 5G technology and the popularization of AI intelligence make online teaching less limited. The online education industry is showing an explosive growth trend. More and more online education institutions are listed for financing, and the market value is soaring. However, in 2019, except for GSX, the latest online learning platforms such as New Oriental, Speak English Fluently and Sunlands, have been in a state of loss. Most of these agencies seize the market by increasing advertising investment, but at the same time, they also bring huge marketing costs, which affect the financial performance of the company. With the enhancement of Matthew effect, large-scale educational institutions occupy a large market through free classes and low-price classes, while small and medium-sized institutions with weak capital strength are often unable to afford high sales costs, facing the risk of capital chain rupture. Taking new Oriental online as an example, this paper analyzes the problems existing in the marketing strategies of online education institutions. It also puts forward suggestions on four aspects, which are target market, differentiated value, marketing mix and marketing mode, so as to make sure that online education institutions can control marketing expenses and achieve profits by improving course quality, expanding marketing channels and implementing precise positioning.

Performance enhancement of Echo Cancellation Using a Combination of Partial Update ( PU) Methods and New Variable Length LMS (NVLLMS) Algorithm

2018 ◽  
Vol 24 (5) ◽  
pp. 66
Author(s):  
Thamer M. Jamel ◽  
Faez Fawzi Hammood
Keyword(s):  
Mean Square Error ◽  
Return Loss ◽  
Performance Enhancement ◽  
Variable Length ◽  
Echo Cancellation ◽  
Convergence Time ◽  
Length Variation ◽  
Mean Square ◽  
Step Size ◽  
Echo Return Loss Enhancement

In this paper, several combination algorithms between Partial Update LMS (PU LMS) methods and previously proposed algorithm (New Variable Length LMS (NVLLMS)) have been developed. Then, the new sets of proposed algorithms were applied to an Acoustic Echo Cancellation system (AEC) in order to decrease the filter coefficients, decrease the convergence time, and enhance its performance in terms of Mean Square Error (MSE) and Echo Return Loss Enhancement (ERLE). These proposed algorithms will use the Echo Return Loss Enhancement (ERLE) to control the operation of filter's coefficient length variation. In addition, the time-varying step size is used.The total number of coefficients required was reduced by about 18% , 10% , 6%, and 16% using Periodic, Sequential, Stochastic, and M-max PU NVLLMS algorithms respectively, compared to that used by a full update method which  is very important, especially in the application of mobile communication since the power consumption must be considered. In addition, the average ERLE and average Mean Square Error (MSE) for M-max PU NVLLMS are better than other proposed algorithms.  

PHYSIOLOGICAL AND HYGIENIC CHARACTERISTICS OF THE HEALTH STATUS OF ADOLESCENTS STUDYING THE PROFESSION DRILLER

2018 ◽  
pp. 18-21
Author(s):  
M.Yu. Stupina ◽  
N.P. Setko
Keyword(s):  
Health Status ◽  
Mental Performance ◽  
Growth Trend ◽  
Biological Adaptation ◽  
Functional Reserves

The article presents data on the features of functional reserves, the level of biological adaptation, mental performance of students by the profession driller. We found that more than half of the adolescents had reduced adaptive reserves of varying severity. Thus, the level of functional reserves, which was reduced relative to the physiological norm, was noted in 89 % of the 1st year, 83.4 % in the 2nd year and 93.3 % in the 3rd year students. In parallel, there was the growth trend to the 3rd year of study from the students number with reduced performance (from 27.6 % to 33.3 %) and an increase by 1.6 times of the students number with a significantly reduced level of performance.

Sign in / Sign up

Export Citation Format

Share Document